chapter 13 evidence of evolution copyright © mcgraw-hill education. all rights reserved. no...

Chapter 13 Evidence of Evolution

Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

Fossil: ©Lou Mazzatenta/National Geographic StockProtoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock

Clues to Evolution Lie in the Earth, Body Structures, and Molecules

Section 13.1

Life on Earth arose 3.8 billion years ago. Changes in body structures and molecules have slowly accumulated through that time, producing the variety of organisms we see today.

Figure 13.2


Section 13.1

Scientists use the geologic timescale to divide the history of the Earth into eons and eras. These periods are defined by major geological or biological events, like mass extinctions.

Figure 13.2


Section 13.1

Researchers analyze fossils, anatomy, and molecular sequences to learn how species are related to one another.

Ge Sun, et al. "In Search of the First Flower: A Jurassic Angiosperm, Archaefructus, from Northeast China,"Science, Vol. 282, no. 5394, November 27, 1998, pp. 1601-1772. ©1998 AAAS. All rights reserved. Used with permission

Paleontology is the study of fossil remains or other clues to past life. Fossils provided the original evidence for evolution.


Section 13.1

Fossils are the remains of ancient organisms.

Figure 13.1

Left fossil: Ge Sun, et al. "In Search of the First Flower: A Jurassic Angiosperm, Archaefructus, from Northeast China,"Science, Vol. 282, no. 5394, November 27, 1998, pp. 1601-1772. ©1998 AAAS. All rights reserved. Used with permission; Wood: ©PhotoLink/Getty Images RF; Embryo: ©University of the Witwatersrand/epa/Corbis; Coprolite: ©Sinclair Stammers/Science Source; Trilobite: ©Siede Preis/Getty Images RF; Fish fossil: ©Phil Degginger/Carnegie Museum/Alamy RF; Leaf fossil: ©Biophoto Associates/Science Source; Triceratops: ©Francois Gohier/Science Source

13.1 Mastering Concepts

What is the geologic timescale?


Fossils Record Evolution

Section 13.2

Fossils form in many ways.

Figure 13.4Compression fossil of leaf: ©William E. FergusonHuman skull and bone fossil: ©John Reader/Science Source


Section 13.2


Figure 13.4Impression of dinosaur skin: ©Dr. John D. Cunningham/Visuals Unlimited Horn coral: ©Robert Gossington/Photoshot


Section 13.2


Figure 13.4Mosquito trapped in amber: ©Natural Visions/Alamy


Section 13.2

Even though fossil evidence is diverse, it is often challenging—or impossible—to find fossils of transitional forms between groups.

Figure 13.3Ammonite: ©Jean-Claude Carton/Photoshot

The fossil record is incomplete, partly because some organisms (such as those with soft bodies) fail to fossilize. Also, erosion and movement of Earth’s plates might destroy fossils.

Fossils Record EvolutionDating fossils yields clues about the timeline of life’s history.

Figure 12.3Section 13.2 Canyon: ©Terry Moore/Stocktrek Images/Getty Images RF

The simpler, and less precise, method of dating fossils is relative dating, which assumes that lower rock layers

have older fossils than newer layers.


Section 13.2

Absolute dating uses chemistry to determine how long ago a fossil formed.

Figure 13.6Woolly mammoth skeleton: ©Ethan Miller/Getty Images

Radiometric dating is a type of absolute dating that uses radioactive isotopes.

Clicker Question #1

Which rock layer (A, B, or C) should have fossils with the most carbon-14?

A

B

C

Flower: © Doug Sherman/Geofile/RFCanyon: ©Terry Moore/Stocktrek Images/Getty Images RF

Clicker Question #2

Researchers used a radioactive isotope with a 25,000-year half-life to date a fossil to 100,000 years ago. The fossil contains ____ as much of the isotope as does a living organism.

A. 1/2B. 1/4C. 1/8D. 1/16E. 1/32

Flower: © Doug Sherman/Geofile/RF


Distinguish between relative and absolute dating of fossils.


Biogeography Considers Species’ Geographical Locations

Section 13.3

According to the theory of plate tectonics, Earth’s surface consists of several rigid layers, called tectonic plates, that move in response to forces acting deep within the planet.

Figure 13.7


Section 13.3

Fossils help geographers piece together Earth’s continents into Pangaea.

Figure 13.8


Section 13.3

Biogeography sheds light on evolutionary events.

Figure 13.9

Animals on either side of Wallace’s line have been separated for millions of years, evolving independently.

The result is a unique variety of organisms on each side of the line.


How have the positions of Earth’s continents changed over the past 200 million years?


Anatomical Relationships Reveal Common Descent

Section 13.4

Two structures are homologous if the similarities between them reflect common ancestry.

Figure 13.10


Section 13.4

All of these animals, for example, have similar bones in their forelimbs.

Figure 13.10

These similarities suggests that their common ancestor had this bone configuration.


Section 13.4

Homologous structures need not have the same function or look exactly alike.

Figure 13.10

Different selective pressures in each animal’s evolutionary line have led to small changes from their ancestor’s bone structure.


Section 13.4

A vestigial structure has lost its function but is homologous to a functional structure in another species.

Figure 13.11Mexican-boa-constrictor: ©Pascal Goetgheluck/Science SourcePython skeleton: ©Science VU/Visuals Unlimited

Vestigial hind limbs in some snake species and pelvises in whales are evidence of these organisms’ ancestors.


Section 13.4

Anatomical structures are analogous if they are superficially similar but did not derive from a common ancestor.

Figure 13.13Salamander: ©Francesco Tomasinelli/The Lighthouse/Visuals UnlimitedCrayfish: ©Dante Fenolio/Science Source

None of these cave animals has pigment or eyes.

These similarities arose by convergent evolution, which produces similar structures in organisms that don’t share the same lineage.

Lack of pigment arose independently in each of these cave animals.

Clicker Question #3

The streamlined shapes of dolphins and sharks evolved independently. The body plan of these two animals are

A. homologous.B. vestigial.C. analogous.D. a product of convergent evolution.E. Both C and D are correct.



What can homologies reveal about evolution?


Embryonic Development Patterns Provide Evolutionary Clues

Section 13.5

Anatomical similarities are often most obvious in embryos. Notice how much more similar human and chimpanzee skull structure is in fetuses compared to in adults.

Figure 13.14


Section 13.5

Adult fish, mice, and alligators have very different bodies. Their evolutionary relationships are more obvious in embryos.

Figure 13.15Fish: ©Dr. Richard Kessel/Visuals Unlimited; Mouse: ©Steve Gschmeissner/Science Source; Alligator: USGS/Southeast Ecological Science Center

How do similar embryos develop into such different organisms? Homeotic genes provide a clue.


Section 13.5

Homeotic genes control an organism’s development. Small differences in gene expression might make the difference between a limbed and limbless organism.

Figure 13.16

Homeotic genes therefore help explain how a few key mutations might produce new species.


Section 13.5

Mutations in segments of DNA that do not encode proteins also produce new phenotypes.

Figure 13.17


How does the study of embryonic development reveal clues to a shared evolutionary history?


Molecules Reveal Relatedness

Section 13.6

Comparing DNA and protein sequences determines evolutionary relationships in unprecedented detail.

It is highly unlikely that two unrelated species would evolve precisely the same DNA and protein sequences by chance.

It is more likely that the similarities were inherited from a common ancestor and that differences arose by mutation after the species diverged from the ancestral type.


Section 13.6

Molecular clocks assign dates to evolutionary events.

Figure 13.20

If a gene is estimated to mutate once every 25 million years, then two differences from an ancestor might arise in 50 million years.


Section 13.6

If a gene is estimated to mutate once every 25 million years, then two differences from an ancestor might arise in 50 million years.

Figure 13.20

Therefore, two species that derived from the same common ancestor 50 MYA might have four differences in the nucleotide sequence of the gene.

Clicker Question #4

Mutations in a gene occur at a rate of one nucleotide every 10 million years. The gene sequence differs by 6 nucleotides between two related organisms. How long ago did these organisms split from a common ancestor?

A. about 2 million years agoB. about 30 million years agoC. about 60 million years agoD. about 120 million years agoE. None of the choices is correct.



How does analysis of DNA and proteins support other evidence for evolution?


chapter 13 evidence of evolution copyright © mcgraw-hill education. all rights reserved. no...

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